1. Field
The embodiment relates to a method for removing moisture from a substrate coated with a transparent electrode.
2. Description of the Related Art
A transparent electrode has been used to manufacture a device such as a thin film solar cell, a thin film transistor liquid crystal display (TFT LCD), an organic electro luminescence display (OELD), a light emitting diode (LED), or a laser diode (LD).
The transparent electrode is coated on a substrate, and is patterned according to a need of each procedure in a process for manufacturing the listed devices. An etching procedure is used at the patterning time. In this case, etch residues pollute the transparent electrode or a substrate. The pollution significantly deteriorates characteristics of a device. Accordingly, a procedure for washing the transparent electrode and the substrate is performed after the etching procedure. A wet cleaning process using deionized water is widely used as the cleaning procedure.
Among the listed devices, for example, in a mass production line of the thin film solar cell, before a silicon thin film is deposited on a glass substrate coated with a transparent electrode, a wet cleaning process using deionized water is necessarily performed so as to remove particles being etch residues remaining on a surface of the transparent electrode or the substrate.
In the case, a transparent electrode coated by chemical vapor deposition (CVD) is a polycrystalline thin film having a structure in which moisture is readily adsorbed on a surface thereof and at an intercrystalline particle boundary. Accordingly, the deionized water used in the wet cleaning process is adsorbed on the surface of the transparent electrode and at the intercrystalline particle boundary.
If moisture such as deionized water remains on the transparent electrode or the substrate, upon deposition of a thin film on the transparent electrode or the substrate for forming the thin film device, adhesion between thin films is deteriorated. Due to this, a thin film deposited on the transparent electrode or the substrate is frequently peeled off therefrom. Such a feature is connected directly with characteristics and yield of the listed devices.
Among the listed devices, for example, in a case of the thin film solar cell, moisture remaining on the transparent electrode is diffused into a silicon layer of a thin film coated on the transparent electrode to reduce an open-circuit voltage, which becomes the cause of deterioration in photo-electronic conversion efficiency of the thin film solar cell. Consequently, it is very important to remove the moisture remaining on the transparent electrode or the substrate in order to manufacture the thin film solar cell with high efficiency and high yield.
For example, in a case of the OELD, an organic layer forming an emission layer may be degraded due to moisture remaining on the transparent electrode or the substrate. This reduces the life of OELD and deteriorates emission efficiency thereof.
Consequently, in a thin film device using the transparent electrode, a method for removing moisture remaining on the transparent electrode or the substrate is very important to improve characteristics of the thin film device.